The USB is an interface that is used to connect a personal computer to a peripheral device. The USB has been almost substituted for the conventional serial port and parallel port. The USB has been used as an interface through which digital data such as a still picture and a low bit rate moving picture photographed by a digital camera is transferred to a personal computer. Generally, in the digital camera, photographed picture data is recorded to a removable storage medium such as a memory card.
In the case that a picture file recorded in the memory card of the digital camera is transferred to the personal computer, if the digital camera has a USB port, when the digital camera is directly connected to the personal computer through a USB cable, the picture file recorded in the memory card can be transferred from the digital camera to the personal computer.
As USB interface's standards for digital cameras, there are standards with respect to mass storage class interface and still image class interface. Through the mass storage class interface, a personal computer recognizes a digital camera as a removable medium. Through the still image class interface, the personal computer recognizes a digital camera as a scanner. Thus, depending on how a personal computer recognizes a device, there are two different classes. The mass storage class interface is prescribed in “Universal Serial Bus Mass Storage Class Specification Overview (Revision 1.1 Jun. 28, 2000)”.
So far, a camera that can use both the interfaces at a time or select one of them has not been released. This is because it was considered that there was no need to provide a camera that deals with both the classes. In addition, when a camera deals with only a single USB interface, the cost and circuit scale thereof can be reduced. In contrast, personal computers can deal with any class. A device driver corresponding to a class of a digital camera is bundled therein. The bundled device driver is installed to a personal computer.
In addition, a digital camera that has a function for recording a plurality of different format files to a record medium is known. For example, a digital camera that can record both a photographed picture (main picture) and an E-mail size picture to a record medium has been proposed. As another example, a digital camera that has a function for recording both a main picture and a voice memo to a record medium has been proposed. Hereinafter, sometimes, a main picture is referred to as main file; a file related to a main file is referred to as sub file.
When the conventional mass storage class interface is used, since a digital camera is recognized as a removable media, it is necessary for the user to manage the directory. For example, a folder “Dcim” is created in a memory card. In the folder “Dcim”, a sub. folder “100 msdcf” is created. In the sub folder “100 msdcf”, for example a JPEG picture file is stored. A file name of a picture file is composed of for example “dsc”+five-digit numeral+extension (that represents a picture compression format (for example, .jpg)). A digital camera has a function for creating both a still picture file and a voice memo, an E-mail picture, or the like. They are stored in other folders. Unless the user knows such a directory structure, he or she cannot easily search and operate a desired file.
In addition, in a digital camera body, a main picture and an E-mail sub file are stored in different folders. Thus, when folders, file names, and record date/time data are compared, a main picture and a sub file can be correlated. When data recorded in a record medium is transferred to a personal computer using the conventional mass storage class USB interface, the directory structure of the digital camera is transferred to the personal computer as it is. In this case, the user should search a sub file related to a main picture file using a folder name, a file name, record date/time data, and so forth. Thus, the user cannot easily know the relation of these files.
Recently, as a higher layer created corresponding to the still image class interface, PTP (Picture Transfer Protocol) has been proposed by PIMA (Photographic and Imaging Manufacturers Association, Inc.). This standard deals with a data transfer system for digital cameras and scanners. In this system, without need to consider the directory structure, the user can easily capture a picture file to a personal computer and select a desired file on the personal computer. For example, the PTP has a function for displaying a thumbnail picture for a picture file. Thus, as a USB interface for digital cameras, to allow the users to easily operate them, it is preferred to use the PTP.
However, in the PTP, data other than picture data (for example, voice data) cannot be recorded from a personal computer to a memory card of a digital camera. In contrast, data other than picture data cannot be captured to a personal computer. In addition, since the PTP is supported by new OSs (Operating Systems), not old OSs. Thus, when only the PTP is used, it is necessary to cause the old OSs to support the PTP. Thus, for example, it is necessary to originally develop device drivers for the old OSs. As a result, the cost rises.
In addition, in the PTP, a directory structure of folders recorded in a record medium cannot be transferred to a personal computer. Picture data and sub files are transferred as same type data. Thus, with data transferred corresponding to the PTP, the user cannot easily know the relation of a main picture file and a sub file.
Therefore, a first object of the present invention is to provide a digital camera that can deal with at least two USB interfaces at the minimum cost.
A second object of the present invention is to provide a digital camera and a data transferring method that use a USB interface through which picture data is transferred regardless of the directory structure of a record medium as with the PTP and that allow the user to easily know the relation of two or more related files on a personal computer.